Common hard disk failures

Electrical Failure

The PCB is the “middleman” of sorts, controlling, communicating and coordinating to read and write data between the hard disk and the computer. As such, if the PCB gets damaged due to power surges or power spikes, you lose access to your data. Frequently, the pre-amplifier circuit of read-write head may also be affected.

Mechanical Failure

Mechanical damage normally arises as a result of impact or wear and tear.
Internal components, like the read-write head and motors, can become faulty without prior warning. The much dreaded head crash could be a by-product of mechanical failure.

Firmware Failure

Firmware is the software program normally only accessible by the disk manufacturers. It is used to do low level disk testing and functions that are directly responsible for the proper functions and healthy state of hard disk.

Without the firmware code, no communication will be possible between the PC system and the hard disk.

Modern disks normally have their firmware codes located on data platters and also the PCB board. If the firmware area of the platter is corrupted, the drive will appear to have failed even all the electrical and mechanical components are still fully functional.

Bad Platter Area

A hard drive platter

This is commonly coined as "bad sectors" which are seen as inaccessible data blocks or sectors during reading or writing operation. The main cause is due to wear and tear of platter surface, head crash, manufacturing defects and tracking errors.

There are various levels of bad sector severity. Depending on the situation, different techniques will have to used to "maximise" the recovery yield.

Complex Failure Model

Most often, hard disk may not fail in just any single mode. The failure could cause by a combination of some or all the failure modes, normally triggering by one to another. For instance, a read write head crash due to mechanical failure could leave to logical file system damage as well as firmware code corruption. Bad sectors development is also a natural by-product under such circumstances.